Premixed and direct-injection spark-ignition piston engines operating on the Otto cycle and direct injection engines operating on the diesel cycle represent the bulk of known engines used for motor vehicles. These engines are popular for a variety of reasons but, primarily, they are widely used because they offer reasonable efficiencies for a wide range of power settings. One major disadvantage for spark-ignition engines is that they must operate in a mode in which the ratio of the fuel mass to the air mass in the engine at the combustion stage is near stoichiometric. Thus, to operate at partial power, the engine must be throttled, whereby the pressure on the intake side must be deliberately reduced in order to limit air mass flow rate. This effectively limits the compression ratio and, in turn, the efficiency of the engines. This fact is the basis for the success of the hybrid-electric propulsion system.
The direct-injection spark-ignition and diesel engines are not as limited by this requirement but these two types of engines have significant emissions problems. The problem of varying the mixture ratio away from stoichiometric is solved using high turn-down ratio combustors in Brayton cycle engines based on gas turbine technology. This is possible because the combustion process occurs in a separate physical area of the engine from the compression and expansion, allowing for only part of the air to be burned in combination with the fuel in a highly controlled way. Having a separate physical area where combustion takes place allows the power levels to be controlled by varying only the fuel flow rate to the combustor. The disadvantage to running the Brayton cycle engines at partial power is explained by the fact that known axial flow compressor and turbine systems are inefficient at off-design operating points.
Another disadvantage of conventional piston engines is that the air is ported to the combustion chamber through valves, which limit the ability of the engine to breathe efficiently and introduce pumping losses even with wide open throttle settings.
To combat these problems, many efforts have been made to develop successful high volumetric flow rate positive displacement compressors of the rotary vane type. Previously known engines of the rotary vane type have substantially depended on intermittent spark-ignition and/or fuel injection in a small volume for combustion. This inherently limits the performance in the same way that piston engine performance is limited by combustion stoichiometry.
Additionally, the sealing of rotary vane devices for high temperature applications such as combustion engines has eluded inventors to date and excessive wear has hampered the success of known rotary vane devices of all types. In order to create a successful rotary vane engine, positive sealing of the vanes must occur along the outer edge of each vane, along the sides of each vane, along the base area of each vane and between the rotor and the case. Without proper sealing, adequate compression and expansion cannot take place. Additionally, the high wear rates associated with the centrifugal forces of known rotary vane engines must be reduced for longevity of the device.
Thus it can be seen that needs exist for improvements to combustion engines and particularly those of the rotary vane type. Additionally, it can be seen that needs exist for rotary vane combustion engines that effectively seal the compression and expansion cavities while reducing component wear, such that an extended service rotary vane engine can be implemented. It is to the provision of these needs and others that the present invention is primarily directed.